vgr926

Well, I know that Acura TLX is supposed to be all about passion and adventure (at least according to Acura), so what I'm about to say must be an equivalent of a sin... I try to hypermile in mine. I have a long freeway ride to work and back, and I'm a scientist by profession, so I try to run experiments on minimizing the gas consumption during my ride every day. Having a trip computer in this car makes this fun because you can do these measurements very quickly.

There was a thread in here a few month ago on what sort of mpg rating TLX owners experienced. There were a lot of images with all kinds of trip computer numbers posted there. Well, based on my limited experience so far, all these numbers mean absolutely nothing because we don't know in which conditions they were produced, and therefore they can't be replicated and they provide very little insight into what the real fuel efficiency of this particular car is. That's why I want to start a new thread to share my experience so far, and see if somebody else was curious enough to do similar measurements.

First, let me make a few general statements:

1) 2.4L TLX is capable of way higher mpg numbers than the EPA values indicate.

2) When I talk about mpg numbers, I mean "freeway/highway mpg". The "city mpg" is a fairly abstract and artificial number, which depends heavily on the road conditions and driving habits, and is only sure to be between 0 and freeway mpg. The only true indication of a car fuel efficiency can be measured when it rolls at constant speed for a long distance, with no traffic interruptions.

3) Even is steady driving conditions, the fuel efficiency is very strongly affected by the car speed. Therefore, it doesn't make sense to discuss the mpg numbers without at least referring to what speed the car was at. Just don't even waste your time: you will be comparing apples to oranges.

4) The second most important factor that affects the mpg ratings is the road surface profile. If you are going downhill, you will always get much better readings then going uphill, because of the gravity. Very often, a road seems visually flat, yet by looking at the instantaneous mpg on the trip computer, you can immediately tell whether you are on a slight up/down slope. As a matter of fact, having a trip computer in this new car really opened my eyes on how three-dimensional roads are! Before, I only memorized left and right zigzags of my daily commute, but now I am also very well aware of all the hills and valleys. I also developed a procedure for taking this variable out of the equation. I pick a relatively flat section of the freeway and do two opposite runs on it: on my way to work and from work. Then, I average the two numbers.

5) There are many other smaller factors that affect the mpg values, for example air temperature, tire pressure, A/C operation (easy to turn off though), engine temperature. I am still trying to quantify this.

6) All my numbers are obtained with: A/C off, audio off, cruise control on, transmission in "Sport" or "Normal". I believe the transmission setting is not important on a freeway because you tend to roll in the last gear anyway.

7) The trip computer numbers are not too far off from the real mpg measured at refills (+/- 1 mpg).

With that being said, here are some preliminary numbers for my 2.4L TLX:

@70 mph: 41-42 mpg, drops to ~39 mpg with 2nd person in car
@65 mph: 45-46 mpg
@60 mph: 50-51 mpg

So these numbers are substantially higher than the EPA highway mpg (35). This makes me curious how exactly the EPA numbers are obtained (although I believe that their highway cycle is not quite pure highway).

It seems possible to reach >60 mpg by driving at constant 45-50 mph on empty roads. That would be cool! I hope to verify this soon. If this is true, you could get over 1000 miles out of a single tank!

justnspace

iTrader: (1)

awesome experiment!!!!

happy hypermilling!

neuronbob

But great experiment. Your post makes exactly the same point as one of Jeremy Clarkson's best Top Gear segments from 2008. In that segment, he compared the mileage of a Prius ( ) being driven flat out, with a BMW M3 (E90 sedan, ) being driven sedately. The M3 famously returned better fuel economy than the Prius. The point was, it's all about HOW you drive rather than WHAT you drive.

Rock on, my friend, in the name of science.

Quandry

Your findings that speed has a direct impact on mpg has been known for many years, and it was the motivating factor to reduce speed limits back in the gas price crisis era. It is an inherent human (maybe mostly male) trait to want to go faster, and damn the cost. Your posting may slow a few people down a bit but the speed will go back up fairly quickly.

Stew4HD

The good ole double nickel Big government control though the good that came from it was we figured out how to make more HP from smaller engines.

I had a '72 Challenger with a 318cu 2-bbl that was rated at 150hp! It was a dog.

vgr926

I don't think that video was a great comparison because they managed to abuse the Prius to the point when they got 17 mpg out of it. But speaking of the Prius, its users seem to report a typical highway mpg of 47-50, and some of them claim that the car has to be driven slowly (like 50 mph) to get there. So I can make a valid claim that in pure highway driving Acura TLX gets better mileage than the Prius!

a77

Keep us posted!

The prius experiment was perfectly fair. The rule was that the Prius was driven flat out and the BMW just tailed it at the same speed. Unrealistic maybe but proved the point that what matters most is how you drive. Another daily telegraph (Times?) test a few years back equally (in)famously pitted a Prius against a 520d BMW for a journey from London to Switzerland. The BMW got better overral mileage, mainly as the Prius was unable to do well in high speed autoroute conditions, where the BMW just sailed along.

I have recorded 5.0 ltrs per 100 kms (47 US mpg) in normal suburban driving over 24 kms in the TLX. But I started on a warm engine and never got held up. Went with the flow - probably 10% over posted speeds. There was a net altitude drop of 500 feet or so. Shows what is possible, but this tank I am at 8.0 (29.5). In my TSX I averaged 7 over 47000 kms. Usually driving more aggressively than right now.

I am looking forward to trips to the cabin in the summer. The TSX would get between 5.7 and 6 over the 500kms there with an average speed of 100 kmh or so (actual speeds ranging from 90 to 140). That's the one trip where I think the TLX' higher gearing ought to pay dividends.

g37guy01

I couldn't disagree more. The point is where you drive and how you drive. When I drove the Prius through the southwest desert I was getting 50+ miles/gallon.


Try driving an M3 and a Prius in mid-town manhattan for one day as taxis and tell me the M3 wins the gas mileage race.

Rocketsfan

lol. Reminds me of the old Texas slogan when they set max MPH on highways to 55 mph. "Fifty-five saves lives!" Saves gas, too. Of course you'll probably piss everybody and their mother off on Texas roads now driving at that speed. Not to mention it may save lives, but get you killed.

My mileage in the winter months has gone down from what I was experiencing in the summer months. I still haven't figured out why. My guess is that the "hot" tire pressure has something to do with it, but not sure what else. The mileage is still great, though. Better than I had expected. I average about 26-28 mph in my city driving during the workweek and have been getting 25.7-28 mpg with the AC/heater on and Normal mode. I've hit 39-41 mpg without even trying on highway/freeway-only trips with the AC and cruise control on in the summer. It's almost time for me take the car in for the first oil change, so we'll see what happens with the fuel mileage after that.

Rocket_man

In Houston, especially on the Beltway 8 toll road, if you're under 70 mph you better get to the right... 'cause I'm coming through . Those driving 55 are just hindering traffic flow.

Back when we switched to 55 many cars still didn't have seat belts and air bags were no where to be seen. Our idea of airbags was my Dad putting his arm in front of me if we came to a sudden stop. Like he was superman or something. Cars are so much safer now. When I was a kid I used to stand on the transmission hump between the drivers and passenger seat and 'surf' down the road. Today my parents would have been hauled off to jail and sent me to a foster home.

Probably the winter blend gas causing the reduced mpg.

acuranj18

My experience in driving Honda and Acura vehicles for many years is that they routinely exceed the EPA highway mpg if driven at a constant speed and without a lot of aggressive maneuvers. The same cannot be said for other brands of vehicles that we have owned.

justnspace

iTrader: (1)

omfg, I hate merging onto beltway 8.
people just dont understand merging.

tlxsteve

Too each his own, but I would rather just sit back and enjoy the ride. I already know my MPG is very good.

Stew4HD

They speed up to close the gap so you can't get in front of them

Davinci547Acura

Totally agree, I consistently got 33-34 mpg on all my 3G TL's at constant interstate speeds and without a 9 speed transmission. The engine basically loafed at 75 mph.

2G TSX consistently got 2-3 mpg less mpg on identical highways because the 4 banger was normally under strain to keep the car weight moving forward especially with head winds.

justnspace

iTrader: (1)

butt butt, if im in front, i have the right of way to merge in front of them!!

omg, pisses me off so bad!

Quandry

The new terminology, at least to me, is zipper merge. It typically applies when two lanes transition into one. Traditionally, moderate drivers stay in the lane that continues and dislike the drivers who take the shorter line and try to merge where the lane ends. Traffic specialists the optimum traffic flow is for both lanes to have the same number of cars with an orderly merge at the end, the sipper merge. The same thing should apply to merging onto the highway. It may take many years for the retraining to occur.

vgr926

Here is an interesting update on my MPG testing:

FUEL CONSUMPTION vs GEAR (or RPM if you like)

HOW I DID IT: Cruise control on a freeway @65 mph or so, drive mode in "Sport+", use paddle shifters to select a gear, watch instantaneous MPG reading on the display (has to be on an even portion of the road with a constant slope).

RESULT: MPG value typically remains constant, regardless of the gear, as long as the engine RPM doesn't exceed ~3000 (coincidentally, this is when you start hearing the growling noise from the engine). At RPM>3000, the fuel consumption goes up quite rapidly (~25% worse at 4000 RPM).

So what does it all mean? Whenever you read a discussion of improved fuel consumption in new cars, a big point is always made about having a million of gears in the transmission, to allow your engine to run at the lowest RPM on a highway. To me, as a physicist, this talk always sounded strange: if you have to apply certain power to propel a car forward (and that means overcoming forces of friction and air resistance), your should expect burning your energy source (gasoline) at the same rate (determined by the engine efficiency), regardless of the gear selection. In low gear, the engine completes its cycles faster, so it will require fuel injections more frequently but the individual injected amount will be relatively small because low gear ratio requires relatively low torque from the engine. In high gear, you inject fuel less frequently but each injection needs to be larger to provide higher torque. So, based on the energy conversion considerations, the fuel consumption shouldn't depend on the gear selection and engine RPM.

That is of course if the engine efficiency is independent of RPM, which, as I understand, is not the case. But I always thought that engines have a specific RPM "sweet spot" where the efficiency is maximized, and the role of the transmission is to keep the engine in this sweet spot. Now, based on my results above (which you can all verify), it seems that this sweet spot is rather large (pretty much anywhere <3000 RPM). So in this case what is the advantage of having an 8-gear transmission that is keeping the engine at 1500-2000 RPM on a highway? Perhaps some of you car experts can educate me.

Quandry

The MPG cannot be the same with the car doing 65 mpg using 6th gear at 4000 RPM and 8th gear at 3000 RPM. In one case the engine is working harder. Move revs mean more gas consumed. The whole idea of additional gears, started with overdrive, is to lower the RPM which saves gas.

Forget the instantaneous MPG. Find a stretch of highway of a few miles. Drive it in Sport+ at some speed with cruise control enabled, in 6th gear, and reset the trip as you start. Take the reading at the end of the set distance. Then repeat the test over the identical road with the car in 8th gear. Compare the MPG and report the results.

vgr926

Quandry: I think you are right. If I drive in the 6th gear at 65 mph, I'm getting MPG in mid-30'th, and on the same road section in the 8th gear I'm getting upper 40th.

So where exactly is the extra energy of the burning gasoline going when you use a lower gear? Is it simply converted to more heat?

Quandry

Primarily heat, but also the effort to spin the engine at a faster rate. Think of the basic physical of a pulley. You may not be able to directly lift a 300lb weight, but attach it to a good pulley and up it goes.

Stew4HD

^Mechanical physics are cool.. leverage using gears and such.

Pocketman

Holy moly! Just ran across this posting after conducting a similar, albeit unscientific, experiment of my own this morning. I experienced ~30 mpg during my overall 20 mile commute. The freeway portion yielded ~47 mpg. This was a simple experiment using on the trip A & B feature of the car. It does however tend to reinforce the OP's findings.

a77

presume your TSX was an auto. My lower geared MT never felt strained at highways speeds and I got a lifetime average (mostly suburban commuting of 33.6mpg US. Highway journeys got as good as 41. So far the TLX is not getting these numbers, but this may be down to very cold conditions since I got it, and winter fuel of course. Will be interesting to see if the TLX' far higher gearing can bring any benefit. In town it doesnt. It ought to on highways.

vgr926

Well, the numbers I got were quite a bit higher than 41 hwy (see above) but it was in fact in relatively mild weather (60's - 80's F). So maybe cold weather does make a difference.

YeuEmMaiMai

I'm now down with a lot of the techniques used in hyper mileling like

taking turns at higher speed to avoid slowing down.

turning your car off at intersections. before anyone complains about well insert car here does it, they were designed to operate that way and will move when you press on the pedal.

riding someone's rear end. I see a lot of people doing that and when you try to do it to me I will move over or if I am already in the first lane, slow down the minimum speed limit. quit being a leech...

Drive your car responsibly and within the common sense and you will get decent gas mileage.